Brake mechanism for automotive vehicles



Aug; 15, 1939 A. A. THOMAS BRAKE MECHANISII FOR AUTOMOTIVE VEHI CLESFi1ed Dec. 1 1936 Patented Aug. 15,1939

U E STATES.

PATENT-I orrics.

1mm MECHANISM roa AUTOMOTIVE VEmC LES

Adolph A. Thomas, New York, N. Y.

Application December 1,1936, Serial No. 113,536

6 Qlaims.

. My invention relates to motor vehicles and its .object is to provideautomatic brake mechanism for the trailers of automobiles whereby thetrailer is always braked in unison with the driving car.

That is to say, the mere operation of the usual brake pedal or lever onthe car ahead automatically operates the brakes on the trailer coupledbehind, sothat the two vehicles can be driven safely at any practicalspeed.

'The recent rage in trailers forpassenger car has induced manufacturersto turn out trailers of considerable size and weight, some models beingveritable houses on wheels. While automobiles with their high-poweredengines can easily pull these trailers, the brakes on the cars cannotthecoupling between the two vehicles. The dangers of such a condition areobvious; the brakes on the automobile will not be able to stop thecoupled vehicles quickly in an emergency, and

the undue strains thus placed upon the coupling may cause the latter tobe torn asunder. An unbraked trailer that becomes uncoupled may entailthe loss of human life.

It is the purpose of this invention to eliminate the above dangers byproviding the trailer with brake mechanism whichis automaticallyoperated iii-unison with the brakes on the automobile.

The driver of the car pays no attention to the trailer brakes, for themere operation of the brake pedal or lever on the 'car automaticallycauses the I trailer brakes .to repeat the action of the auto brakes; Ina preferred formof my invention the variable pressures applied to theauto brakes are automatically duplicated in the trailer brakes, so

I that the trailer always -slows down orstops synchronously with the carahead as if it were an the accidental uncoupling of the trailerautomatie cally puts the trailer brakes onfull, so that the trailerstops almost instantly even on a hill, thereby preventing fatalities, Atthe same time the uncoupling of the trailer automatically sets oil asignal in front of the driver, suchas a 'with such devices.

red light or a bell, so that the'driver can stop the car and-return tothe trailer.

The various novel features and practical advantages of my invention willbeunderstoodfrom a description of the accompanying drawing, in which 1illustrates diagrammatically an electric system for automaticallyoperating the brakes on a trailer in unison with the brakes on thedriving car; and

Fig. 2 is a detached view of a mechanical trailer brake operatedelectrically.

The dotted outlines l and [2 represent a motor vehicle and a trailercoupled together 'at' l3.

These parts are indicated in a diagrammatic way only, for any type orconstruction of motor car, trailer and coupling maybe used. For thepurpose of description we may assume the part I II to be a passengerautomobile and the part l2 to be a trailer fitted out for housekeepingwhile travelling. The coupling l3 may be of any practical design,usually including a swivel joint, and it will not be necessary to showor describe any details thereof, since they form no part of thisinvention. a

The. automobile II) has the usual brake pedal l4 pivoted at, I5 to aconvenient part it vof the chassis. A coil spring l1 normally holds thepedal l4 raised and returns it from depressed or braking positionupon.release. I have assumed that the motor car lll'has hydraulic brakesof the conventional type, indicated diagrammatically at I8 for the frontbrakes and at IQ for the rear brakes. Oil piping 2ll2l leads from themaster 011 cylinder 22 to the hydraulic actuating mechanism of eachbrake, as will be understood by those familiar Thepiston 23 operating incylinder 22 is suitably connected to the brake pedal I, this connectionbeing indicated for simplicity by .a link 24 pivoted to the pedal at25-. When the pedal M is pushed down, the piston 23 forces oil into thehydraulic brakes l8l9, this pressure increasing with the downwardmovement of the pedal. I need not say anything more abouttheconstruction and operation of the'brakes con-- trolled by pedal l4,because that is a matter of common knowledge among those familiar withthe technical side of automobiles. r

The wheels of the trailer l2 are also equipped with brakes, eitherhydraulic ormechanical, both forms being shown in the drawing by wayoif.example. vIn Fig. 1 eachhydraulic brake com.-

prises a drum 26, a pairof brake shoes 21 pivoted to the drum at 28, anda pair of pistons 29 movable in a small oil'cylinder "for spreading thebrake shoes, which are retracted to inoperaltive position by a coilspring 3|. This simplified brake construction is intended to beillustrative of any practical form of hydraulic brake, and may beconsidered applicable to the brakes |8-|9 on the car I. The circularoutline 32 is supposed tobe a duplicate of the brake mechanism justdescribed, and there are as many brakes on the trailer as safetyrequires, preferably one for each wheel and certainly one for each rearwheel. A master cylinder 33 on the trailer supplies oil or othersuitable liquid through piping 34-35 to the individual brake cylinders30, so that the pistons 39 of all brakes are operated simultaneously andat equal pressures when the piston 36 is pushed into its cylinder. Thepressure of the brake shoes 21 against their respective drums 26 dependsupon the force actuating the piston 36.

A solenoid coil 31, suitably supported on the,

trailer, has a movable magnetic core or plunger 33 connected to the freeend of an arm 39, which is pivoted at 49 to any convenient part of thetrailer frame. The piston rod 4| is connected to arm 39 in any practicalway, as by means of a pair of spaced pins or lugs 42, which may carrysmall antifriction rollers. The same form of connection may he usedbetween the extension 43 of plunger 39 and the arm 39. A contracting.coil spring 44 normally holds the arm 39 against a fixed stop 45, sothat the piston 36 and solenoid core 33 are normally in outermost orinoperative position. When the coil 31 is energized (as presently tobeexplained), it draws in the magnetic plunger 39 and thereby actuates thearm 39 to force the piston 36 farther into the oilcylinder 33. As aresult, oil is driven into the brake cylinders 33 to press the shoes 21against the drum, and the shoes are held in braking position as long ascoil 31 remains energized. Upon de-energization of the coil, spring 44instantly restores the parts to normal position,'as shown, therebyreleasing the brake shoes.

' The braking pressure exerted by the actuated shoes 31 depends upon thestrength of the electric current that energizes coil 31, so that bycontrolling this current strength it is possible to control the variableoperation of Y the trailer brakes. Y I shall presently describe meansfor doing that automaticallyby the variable braking movements of pedall4 on the driving car. When coil 31 is first energized, the initialshock imposed on arm 39 by the sudden inward pull of core 39 is absorbedor cushioned by the dash-pot action of piston 36 in cylinder 33, and Imay supplement that cushioning effect by making the cylindrical core 33operate in the coil like the piston of a dash-pot. or, the steel arm 39may be slightly flexible at its free end to absorb the initial jerkexerted on the arm when the current first surges through coil 31. Infine, the electromagnetic actuating mechanism for the brake piston 36 isso. constructed that it produces a smooth movement of the piston andtherefore of the brake shoes 31. I

I will now describe the electric connections for automaticallycontrolling the brake coil 31 on the trailer by the movements of brakepedal on the automobile. An arm 46 carrying an insulated contact 41 isoperatively connected with pedal I4, and for convenience of illustrationI have shown the arm mounted directly on the pedal, as indicated at 46'.A stationary resistance coil 43 is suitably supported so'as to beengaged by the slidable contact 41 when the brake pedal I4 is operated;this contact being preferably a spring piece with a rounded end adaptedto slide easily over the resistance element 43. The supporting arm 46may be a spring finger which holds the contact 41 pressed against themember 48 during the rocking movements of pedal 4. In the normal orinoperative position of the pedal, as shown in Fig. 1, the contact piece41 is out of engagement with resistance element 43, whereby the circuitof the rheostat is normally open. An insulated button 43 or the like onthe underside of arm 46 rests on the resistance 48 to hold the arm awayfrom the resistance when the contact 41 is in neutral position. If thearm 46 itself is of insulating material, the insulated piece 49 is notneeded. When the pedal I4 is fully depressed, the contact 41 is inposition 41 at the other end of the resistance member 48, which is nowshorted or at minimum ohmic value,.as willmore clearly appear when Idescribe the electric circuits. In the broad aspect of my invention, anypractical form of rheostat may be used, and the contact 41 may beoperatively connected with any suitable part that moves in synchronismwith the brake pedal 4.

Between the automobile I0 and the coupled trailer l2 there is anelectric plug 5|| which consists of two interfitting members 5|53adapted to be pulled apart. These plug members may be molded ofinsulating material and are so shaped inside as to support a number ofelectric contacts. The plug member 5| carries three contacts 53, 54 and55. The contact 53 is a short rod or stud projecting into plug member52, and the contacts 54-55 constitute a normally open switch, thecontact 55 being a spring finger normally out of engagement with contact54. The other plug member 52 carries two switch contacts 5G-51 and aninsulated peg orstud 53 arranged to project into plug member 5|. Thecontact56 is a spring finger normally in pressure engagement 0 withcontact 51, so that the contacts 56--51 constitute a normally closedswitch. When the plug 7 members 5|-52 are fitted together, the roundedhead of contact rod 53 strikes the free end of spring finger 56 andforces it away from contact 51. At the same time the head of theinsulated peg 58 engages the spring finger 55 and holds it pressedagainst the contact 54. In other words,

as long as the plug members 5|--52 remain assembled, the switch 54-55remains closed, the switch 56-51 remains open, and the engaging contacts53 and 56 form a closed switch. when the plug sections 5|--52 are pulledapart, the contacts 53 and 56 break circuit, switch arm 55 springs open,and switch arm 56 snaps closed. 55 The plug sections 5|--52 may be heldtogether with suilicient frictional force by the engagement of the rigidpins 53 and 58-with the spring fingers 55 and 55, it the engagingsurfaces-areproperly shaped. Qtherwise, a releasable friction m lock maybe provided to keep the plugsections 5| 52 firmly together until apredetermined separating force is applied. For example, one or morespring latches 59 attached to one plug section' engage in notches 63 inthe other section. 55 A sudden jerk on the assembled plug sections (aswhen the coupling |3 breaks) causes them to separate and dangle fromtheir cords the member 5| remaining on the automobile and the member 52on the trailer.

A source of electric energy 6| on the automobile may be the storagebattery or the generator, and for convenience I shall refer to it as abattery. One side of battery 3| is grounded at 53 to the metal frame ofthe car and the other side is con- 15 nected by conductor 63 to one endof the rheostat resistance 48. A wire 64 connects the insulated rheostatcontact 41 with jack 53 in plug member 5|, and a wire 65 on the trailerconnects the hicles. If that is not found practical in any particularcase, the points 62 and 66 are electrically connected by a separatewire. The grounded side of coil 31 is connected by conductor 61 to oneside of a battery 68 on the trailer, and the other side of this batteryis connected by conductor 69 to switch contact 51 in plug member 52. Thecon ductor' 61 may include a suitable hand switch 16.

. which is closed before the trailer starts on a journey and is leftopen to save current when the trailer is not in use as a conveyance. Itshould be noted that neither side of battery 68 is grounded, so that thegrounded point 66 of coil 31 has nothing to do with the trailer batterybut only with the grounded battery 6| on the driving car. The reason forthis will be clear when I describe the operation of the system.

In a convenient place near the driver of the car there is mounted asuitable alarm signal 1|, which may be audible or visible, such as a redlight or a small electric bell or a combination of the two. If a lampsignal is used, it may be mounted on the instrument panel in front ofthe driver. One side of the electric signal 1| is grounded at 12 and theother side is connected by conductor 13 to a movable switch arm 14pivotally supported at 15. The arm 14 may either be a magnetic bar orcarry an armature 16 arranged to be held against the magnetic core 11 ofcoil 18 when the latter is energized. One end of coil 18 is connected bywire 19 to conductor 63 or otherwise to one side of battery 6|, and theother end of the coil goes to the movable switch member 55 by way ofconductor 80.

. The contact 54 in plug member 5| is grounded, as

indicated by wire 8| which is connected to the I serted in conductor 13,so that the alarm signal member 52.

1| can be thrown out of circuit when not needed.

While the alarm signal 1| is not absolutely necessary, it is a goodthing to have, as presently will be understood.

In actual practice the three wires 64868l I connected to plug member 5|are'preferably made into a single cable, and the same applies to the twowires 65-69 connected to the other plug These two cables constituteflexible cords between which the assembled plug sections 5l52 aresuspended with suflicient play to take care of all relative movementsbetween the coupled vehiclesduring travel. It is only when the trailerhappens to break away that the plug sections 5l52 are pulled apart, andthen each plug section dangles from its cable. Only a short length ofthe cables need be free for that purpose.

The automatic trailer brake system above described operates as follows:As long as the trailer I2 is coupled to the driving car III, the plugmembers 5l52 remain assembled and form an electric coupling orcontrolling connection between the brake pedal M of the car and thebrakes of the trailer. When the pedal I 4 is in normal or inoperativeposition, the rheostat contact 61 is out of engagement with resistanceelement 46, so that the coil 31 on the trailer remains de-energized andthe trailer brakes are ofi, the same as the auto brakes. When thedriverpresses down on pedal M to operate the car brakes |8|9, the firstmovement of the pedal carries the contact 41 into engagement with theadjacent end of resistance 48, whereby the circuit of coil 31 on thetrailer is closed as follows: Battery 6|, wire 63,

resistance 48, contact 41, wire 64, closed contacts 53 and 56 in' plug50, wire 65, coil 31, and to the grounded side of battery 6|. Theenergized coil 31 pulls in the plunger 38,which actuates the arm 39 andthereby forces the piston 36 inwardly. As a result the brake shoes 21are hydraulically actuated to braking position.

It should be noted that a slight movement of pedal M from normalposition leaves most of the resistance 48 in the circuit of coil 31, sothat the energizing current is at minimum strength and causes the piston36 to exert a correspondingly low hydraulic pressure against the brakeshoes 21. When the brake pedal I4 is pushed in to final position, aswhen the brakes l8-I9 are to be put on at full strength, the rheostatcontact 41 is in position 41 where it cuts out the resistance 48 andpermits the full strength of the energizing current to pass through coil31. In that case the piston 36 is forced into its cylinder at maximumpressure and the brake shoes 21 function at maximum braking power. Inall intermediate positions of brake pedal M the movable contact 41 soadjusts the value of resistance 48 in circuit that the variablepressures applied by the driver to the car brakes |8|9 are automaticallyduplicated in the trailer brakes by meansof coil 31 and the associatedmechanism. That is to say, the variable braking movements imparted topiston 23 by means of pedal M are automatically transmitted to thebraking piston 36 on the trailer, so that the trailer brakes operate assmoothly as the auto brakes. Since the plunger 38 of coil 31 acts uponpiston 36 through increased leverage, the strength of the energizingcurrent in the coil need not be i very great. a

It will be clear from the preceding description that the brakes on thetrailer always operate automatically in unison with the auto brakes, notonly as to time but also as to the variable braking' eifects applied bythe driver. This unitary operation of the auto brakes and trailer brakesrelieves the coupling l3 and the auto brakes |8-|9 of undue strains intheslowing down and stopping of the vehicles, so that the coupledvehicles (no matter how heavy the trailer) can be stopped as easily as asingle automobile. This is essential to the safe operation of traileredcars on highways. 7

There is another danger in the operation of automobile trailers, andthat is the danger of the trailer breaking loose. No matter how strongthe coupling between the vehicles may be, there is always thepossibility of the coupling becoming accidentally disabled, especiallywith heavy trailers. If that-should happen on a sloping highway, therunaway trailer would not only endanger the lives of its occupants butwould be a meance to other vehicles. To avoid such disasters myinvention provides means for automatically stopping the trailer when itbecomes disconnected. Should the coupling l3 break or separate, the plugmembers 5l52 are pulled apart, so that switch 56-51 instantly closes andswitch 5l55 opens. The closing of switch 56-451 closes the circuit ofbattery 68 through coil 31, which is thus energized to full strength andcauses the brake shoes 21 to be applied at. maximum' pressure. Thetrailer is therefore stopped almost at once and is held safely brakedeven on a slope, so that no danger results. At the same time the openingof switch 54-55 de-energizes coil ll, thereby releasing the switch arm Hwhich is pulled against the contact #2 and closes the circuit oi thealarm signal H. The driver/of the car is thus instantly notified of thetrailers breaking loose, so that the car will not go on without thetrailer, as might otherwise happen. The signal H thus acts as anautomatic check on the condition of coupling It. The brakes of theuncoupled trailer can be released by simply opening the hand switch I0.

The automatic braking operations above described are the same withmechanical brakes. Thus, if brakes like that shown in Fig. 2 are used,the pedal H on the car operates the cam I. to spread the brake shoes 81,as will be understood without further explanation. On the trailer brakesthe cam is operated by a solenoid coil II and its plunger 09. What hasbeen said about coil 31 applies to coil 88. When the auto brakes are setby the emergency brake lever, the automatic operation of the trailerbrakesis the same as when the brake pedal l4 is pushed in to the limit.The particular construction of brake used on the car and its trailer isnot material, it being understood that only brakes of approved typewould be installed.

It will be seen from the foregoing explanation of my invention that Ihave provided comparatively simple mechanism for the automatic controlof trailer brakes so as to make travel by trailer more safe. Thismechanism is readily installed at little cost on any automobile andtrailer, and its operation is reliable to the point of certainty, forthere are no weak and delicate parts liable to break or get out oforder. In referring to the vehicles III and I! as an automobile andtrailer assembly, I include not only passenger vehicles but any otherpractical kind of driving car and trailer. For example, the trailer maybe a big moving van or other type of freight vehicle coupled to adriving truck which need be little more than an automotive chassis. Insome cases there may be more than one trailer coupled in tandem to thedriving vehicle, and each trailer will be controlled in the mannerpreviously described for a single trailer.

Although I have shown and described a specific form of mechanism, myinvention is not limited to the details set forth, for it embodiescertain features of fundamental novelty and various modifications arepossible within the scope of the .6 appended claims.

I claim as my invention: 1. In an automobile and trailer assembly, the

combination of hydraulic brake mechanism on each vehicle, a brake pedalon the automobile, and means for simultaneously operating both of saidhydraulic brake mechanisms in response to the movements of said pedal,said brakeoperating means including an electric connection between thecoupled vehicles.

2. In an automobile and trailer assembly, the combination of hydraulicbrake mechanism on each vehicle, a brake pedal on the automobile,

and means for simultaneously operating both of said hydraulic brakemechanisms in response to the movements of said pedal, saidbrake-operating means including an electric connection between thecoupled vehicles, said connection comprising two separable parts, onepart being carried by the automobile and the other part by the gizingsaid solenoid to regulate the working pressure of the brake.

4. In an automobile and trailer assembly, the combination offluid-operated brake mechanism on each vehicle, a brake pedal on theautomobile, a switch operated by said pedal, and means forsimultaneously operating both of said brake mechanisms in response tothe movements of said pedal, said means including a solenoid on thetrailer energized by said switch and fluid power means controlled bysaid solenoid.

5. In an automobile and trailer assembly, the combination offluid-operated brake mechanism on the automobile, a brake pedal on theautomobile for controlling said mechanism, fluidoperated brake mechanismon the trailer including a power cylinder, a solenoid on the trailer forcontrolling said power cylinder, and a switch operated by said pedal forenergizing said solenoid.

6. In an automobile and trailer assembly, the combination offluid-operated brake mechanism on the automobile, a brake pedal on theautomobile for controlling said mechanism, a switch operated by saidpedal, fluid-operated brake mechanism on the trailer, and means forcontrolling said trailer brake mechanisni by the operation of saidpedal, said means including an electromagnetic device on the trailerenergized by said switch and a hydraulic piston operatively associatedwith said device.

ADOLPH A. THOMAS.

